Limit switch for electric-driven hoists



R. E. RICE.

LIMIT SWITCH FOR ELECTRIC DRIVEN HOISTS.

APPLICATION FILED AUG.16, 1919.

ma ma I Patented y 25, 1922.

, 2 SHEETS-SHEET I.

lhvenfor ROY 5. Rice W/TI'IGSS Aim/72616 R. E. RICE.

LIMIT SWITCH FOR ELECTRIC DRIVE N HOISTS.

APPLICATION FILED AUG. 16, 1919.

1,423,624. Patented July 25, 1922.

2 SHEETS-SHEET 2.

ROY E. RICE, OF IB UCYI UUS, OHIO, ASSIGNOR TO ROBERTS & SGRAEFER COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

I Specification of Letters Patent.

Patented July 25, 1922.

Application filed August 16, 1919. Serial Ito; 318,018.

To all whom it may concern Be it known that I, ROY E. B ron, a citizen of the United States, residing at Buoyrus, 'iif'the county of Crawford-and State of Ohio, have invented a certain new and useful Improvement in Limit Switches for Electric-Driven Hoists, of-which the following is a specification.

My invention relates to limit switches for electrically driven hoisting machines, wherein it is desired to limit the excursion of the hoist.

Such hoists are common in coal-handling machinery wherein the hoist is positioned within a tower and the material to be handled is raised to a point at or near the top of the tower and then dumped. In such hoists it occasionally happens that after the hoisting drum and so arranged that it will be automatically tripped and the power for the hoisting motor cut 01?,- in case the bucket overruns the upper limit of its excursion.

My invention is illustrated more or less diagrammatically in the accompanying drawings, wherein- Figure l is a front elevation; and

Figure 2 is a side elevation of Figure 1.

Like parts are indicated by like characters throughout.

A is a base board adapted to support my limit switch mechanism and it is secured to the hoisting drum housing or frame.

B is the hoist drum shaft and carries in. its end the pin B which lies within the slot B of the crank arm B This arm is mounted upon the shaft B and journalled in the base board A. It carries on its other end the pinion B which is in mesh with the gear wheel C,carried upon the shaft which is secured to the base board'A. The gear wheel C has in it the segmental slot C which is concentric with it. C C are stops adjust-ably positioned within the slot C D is a switch base mounted upon the base board A. D is a switch controller arm pivotally mounted at D upon the base D. D is a coil spring.

E is a spring switch arm secured to the controller arm D through the insulated connection E It has the contact face E adapted to contact the pole E which is con nected to any suitable power source E here indicated diagrammatically. E is a similar pole similarly connected to the power source.

F is a lever pivotally mounted on the base D at F and pointed at its lower end, as at F to engage a notch in the end of the switch controllingarm D It is connected to the controller arm D by the toggle joint The switch shown is in the power line of the hoisting motor.

Although I have shown my invention applied to an electric hoist, it is obvious that it might equally well be applied to any apparatus of limited excursion wherein the ings be regarded as in a sense diagrammatic.

The use and operation of my invention are as follows:

When the drum shaft revolves it carries with it by means of the slot and pin connection the small pinion and 'causes it to rotate. This, of course, rotates the gear wheel with which it is in mesh. The ratio between the pin and the gear wheel in the present case is preferably 10 to 1, and the parts are so proportioned that the upward excursion of the bucket of the hoist is completed during less than one revolution of the large gear wheel. The switch parts are normal in the position shown in Figure 1. The trip lever being exactly upright, it resists a tendency of the spring switch arm' the switch to fly open. This. of. course, disconnects the current and at once and positively stops any further hoisting.

I claim 1. A limit switch for electric hoists comprising a switch element adapted normally to be in operative position, yielding means adapted to move it into inoperative position, a member, pivoted in unstable equilibrium, adapted to resist said yielding means, and means for tripping said member after a predetermined excursion of said hoist.

2. A limit switch for electric hoists comprising a switch element adapted normally to be in operative position, yielding means adapted to move it into inoperative position, a member, pivoted in unstable equilibrium, adapted to resist said yielding means, and means for tripping said member after a predetermined excursion of said hoist, comprising a wheel rotated by said hoist, and having means thereon for contacting said member.

3. A limit switch for electric hoists comprising a switch element adapted normally to be in operative position, yielding means adapted to move it into inoperative position,

a member, pivoted in unstable equilibrium, adapted to resist said yielding means, and means for tripping said member after a predetermined excursion ot said hoist, comprising a wheel continuously driven by the hoisting mechanism and so proportioned that a pre-determined rotation of said wheel is accomplished during one complete excursion of the hoist.

4. A limit switch for electric hoists comprising a switch element adapted normally to be in operative position, yielding means adapted to move it into inoperative position,

a member, pivoted in unstable equilibrium,

sist said yielding means and means for.

throwing said member out of equilibrium after a predetermined excursion of said hoist.

6. A limit switch for electric hoists comprising a switch element, yielding means tending to move it into an operative position, a member pivoted in unstable equilibrium, adapted, when in such position, to

resist said yielding means and means for throwing said member out of equilibrium after a predetermined excursion of said hoist, said member being so pivoted that the :t'orceof the yielding means is normally directed axially therealong and through the pivot point.

7. A limit switch for electric hoists comprising a switch element, yielding means tending to move it into an operative position, a member pivoted in unstable equilib rium, adapted, when in such posit-ion, to resist said yielding means and means for throwing said member out of equilibrium after a predetermined excursion of said hoist, said member being so pivoted that the force of the yielding means is normally directed axially therealong and through the pivot point, the switch element being notched on its upper surface to engage the lower end of said element when in unstable equilibrium.

8. A limit switch for electric hoists comprising a switch element, yielding means tending to move it into an operative position, a member pivoted in unstable equilibrium, adapted, when in such position, to resist said yielding means and means for throwing said member out of equilibrium after a predetermined excursion of said hoist, said member being so pivoted that the force of the yielding means is normally directed axially therealong and through the pivot point, the switch element being notched on its upper surface to engage the lower end of said element when in unstable equilibrium, the switch element and said member being pivotally secured to each other.

In testimony whereof, I affix my signature in the presence of two witnesses this 29th day of July, 1919.

n. RICE.

lVitnesses A. F. l'lULL, Hanonn F. BnLLnn. 

